Polycarbonate is a thermoplastic resin having an aromatic polycarbonate ester with excellent mechanical properties, self-extinguishing property, dimensional stability, thermo-stability and transparency. Due to these excellent properties, polycarbonate has become an exemplary engineering plastic, with increasing use in the visible parts of electrical and electronic products, optical discs, automobile parts and the like.
The scope of use of polycarbonate has further increased recently. Research is being carried out to improve the properties of polycarbonate and to use polycarbonate in a variety of fields.
For example, there has been research directed to the modification of the properties of polycarbonate by copolymerization of more than two types of diols having different structures and by including polymers, the structures of which are different from the diols, in the main chain of the polycarbonate. For example, Korean patent application No. 2009-0035031 is directed to a resin composition stated to improve the chemical resistance and the fire retardant property of a polycarbonate by copolymerization of a specific structure with the polycarbonate.
Much research has focused on efforts to improve the limited chemical resistance of polycarbonate. There have also been efforts to address the problem of impairment of its mechanical properties due to the penetration of diluent solvents inside a paint while coating, if a polycarbonate resin is being used as a visible part of electrical and electronic products. In order to solve the problem of impairment of mechanical properties of the polycarbonate, efforts have been made to improve the physical properties of the polycarbonate by blending the polycarbonate with other thermoplastic resins.
Although the chemical resistance of the blended polycarbonate can be improved, the impact resistance or transparency may not be improved. For example, U.S. Pat. No. 4,188,314 is directed to an article of polycarbonate and copolyester having improved chemical resistance, but sufficient impact strength could not be obtained by the method used therein. U.S. Pat. No. 4,634,737 is directed to a resin composition including a copolyester-carbonate ester containing about 25 to about 90 mole percent ester bonds, a polyester and an olefinic polymer, such as an olefin acrylate copolymer. This composition can exhibit improved chemical resistance but exhibits very low transparency.
There have also been efforts to improve the chemical resistance in the main chain of the polycarbonate by introduction of another polymer. For example, research on a polycarbonate comprising a polysiloxane structure has been undertaken. In Korean patent application Nos. 2006-0058195 and 2007-0071592, the chemical resistance of the polycarbonate was attempted to be improved by blending the same with a polyester or polysulfone resin. An improvement in the polycarbonate was obtained by including the copolymer of a specific chemical structure into the polycarbonate in U.S. Pat. No. 5,401,826. However, in this case as well, although the chemical resistance and impact resistance were improved, there was an impairment of the transparency.
Accordingly there is a need for a polycarbonate resin with excellent impact strength, chemical resistance and transparency.